It is possible to use Antialiasing in Multitexture mode?
Make sure Blender's interface is set to "Blender Game" (usualy in the top of the blender window):


Then go to the "Render" settings in the properties panel. Under "Standalone Player" you can set the antialiasing samples:


If you also want to enable Antialiasing in the viewport, which also affects the embedded player, you have to set it in the user preferences. Press [Ctrl+Alt+U] to open the User Preferences window. Then go to System and set Multisample to your desired AA factor. 
You may have to restart blender for this setting to take effect.